Electro-magnetic devices



Nov. 26, 1957 W.4DE FLIGUE ETAL 2,814,764

ELECTRO-MAGNETIC DEVICES Filed Ja n. 7, 1955 ELECTRO-MAGNETIC DEVICES Wladimir de Fligu and Paul L. Lavalle, Paris, France; said Lavalle assignor to said do Fligu Application January 7, 1955, Serial No. 480,554

; Claims priority, application France January 20, 1954 8 Claims. (Cl. 317--165) An electromagnetic device comprises, in its most usual form, a magnetic field and an exciting winding to produce the field.

When the winding is to be subjected to the action of currents, and these currents are of high strength, it is sometimes considered desirable to use as the exciting winding a single conductor, which is substantially equivalent to an exciting winding of a single turn.

However, it may happen that with currents of even greater strength the magnetic induction proportional to the number of ampere turns generated by the said single turn is excessive for a given magnetic field, which makes it necessary to reduce the excitation of the electromagnetic device by employing shunts for the direct current and current transformers for the alternating current.

The present invention has for its object to provide an electromagnetic device by means of which it is readily possible to control the value of the magnetic induction produced by a control current, the strength of which is not limited by the saturation of the magnetic circuit.

In the device according to the invention a conductor, through which the entire exciting current flows, extends on both'sides of the main element of the magnetic circuit, while being directed in the same direction and being divided into two unequal parts. Thus, the said element of the magnetic circuit is differentially excited.

In most magnetic circuits, branches of the magnetic circuit extend around the main element or core, the said branches being intended to close the said magnetic circuit and to concentrate the flux in the air gaps. By reason of this arrangement the single conductor extends through said circuit and induces in the whole circuit a flux proportional to the total current. This flux may be additive or subtractive in relation to that of the main element or core, depending upon the direction of the resultant of the first differential magnetic excitation, that is to say, upon whether the right-hand part or the left-hand part of the conductor has the larger cross-section.

In a preferred arrangement of the invention, the division of the current circuit is produced by providing a hole in a solid conductor through which the whole current flows so that the conductor is divided into two or is forked, the hole being situated asymmetrically and the main element of the magnetic circuit extending entirely therethrough.

Preferably, the main element of the magnetic circuit is a central portion of the said circuit, so that the two parts of the current circuit are both surrounded by symmetrical branches of the magnetic circuit, whereby the manufacture is simplified because only the conductor need be asymmetrical.

Since the forked conductor as a whole may be regarded as being surrounded by a magnetic circuit, the resultant induction of the circuit may be controlled by adjusting the reluctance of these magnetic elements, taking into account the differential excitation referred to.

The description which follows with reference to the United States Patent accompanying drawing, which is given by way of example only, will enable the invention to be more readily understood. The drawing diagrammatically shows in perspective an electromagnetic relay device constructed in accordance with the present invention.

In the drawing the magnetic device comprises a U- shaped member 1 provided with a central core 2, and an armature 3 subjected to the action of the return spring 4. r

The magnetic circuit therefore comprises three branches one of which is formed by the right-hand arm of the U-member and the core and is closed by the righthand part of the armature, the other by the left-hand arm, the core and the left-hand part of the armature, and the third by the member 1 and the whole of the armature 3.

These three circuits are excited by the solid conductor 5, through which the entire current strength passes and which has a transverse hole 6 which is asymmetrical in relation to conductor 5. The core 2 passes through hole 6.

The current passing along conductor 5 is divided into two parts since at the hole 6 the conductor is forked, the current strength being substantially proportional to the sections a.c and he being the thickness of the conductor 5 and a and b the shortest (unequal) distances between the edges of the conductor and the edge of the hole 6. Each of these two current paths produces magnetic induction in the magnetic circuit, the magnetic field induced in core 2 by the two current paths obviously being in opposite directions. In addition, the total current also produces a magnetic induction in the magnetic circuit surrounding the conductor.

The value of the magnetic attraction to which the armature is subjected depends upon the resultant of these different inductions, which can be controlled, on the one hand by varying the position of the hole 6 and on the other hand by selecting the value for the reluctance of each of the current paths. These values may be determined by the choice of the length of the branches of the fixed part of the magnetic circuit, that is to say, by the dimensions of the air gaps separating the terminal faces 1a, 1b and 2a from the armature. When these faces are at different levels, non magnetic wedges may be disposed on the said faces for the correct application of the armature to the magnetic device.

The example illustrated concerns a relay, but it must be understood that the invention is applicable to all magnetic circuits subjected to the action of heavy currents in which the magnetic induction generated is utilised for any desired purpose, for example in the case of current transformers.

It will be understood that modifications may be made in the embodiments hereinbefore described, notably by substitution of equivalent technical means, without departing from the scope of the present invention.

What we claim is:

1. An electromagnetic device comprising a magnetic circuit having a core element and a portion associated therewith to conduct magnetic flux, and an electrical conductor having two parts of unequal cross-sections extending on both sides of said core element, whereby said core element is differentially energized by the currents flowing through said two parts.

2. Device as claimed in claim 1, wherein the magnetic circuit comprises three interconnected branches in the shape of an E, the core element forming the medium branch of the E.

3. Device as claimed in claim 2, wherein the two lateral branches of the E belong to magnetic paths having different magnetic reluctances.

4'. An electromagnetic device comprising a magnetic circuit having a coreelement and a portion associated therewith to conduct magnetic flux, and an electrical conductor having an asymmetrical transverse passage extending therethrough and dividing said conductor into two parts of" unequal cross-sections, said core element being positioned within said passage.

5. Device as claimed in claim 4*, wherein the conductor has a generally rectangular cross-section and the passage extends between twoopposite sides thereof in a direction substantially perpendicular thereto.

6. An' electromagnetic relay device comprising an armature, a core magnetically associatedv with said armature toattract the same, and an electrical conductor having two parts of unequal cross-sections extending on bothsides of said core, whereby said core is difierentially a1. energized by the currents flowing through said two parts. 7. Device as claimed in claim 6, wherein the core is in the shape of an E with three generally parallel branches, the central branch being disposed intermediate the two parts of the conductor and the lateral branches extending outside said parts.

8. Device as claimed in claim 7, wherein the air gaps are formed between the armature and the ends of the three branches, said air gaps being of ditferent sizes.

References Cited in the file of'this patent UNITED STATES PATENTS 2,061,920 Piifath Nov. 24, 1936 2,082,121 Rypinski June 1, 1937 2,450,973 Lingel Oct. 12, 1948 

